X-ray fluorescence analysis of elemental content of snake venoms

Snake venoms contain a variety of different components, most of which are protein and peptide toxins. Although certain metal ions are known to be integral parts of several important venom enzymatic toxins, the elemental content of snake venoms has received scant attention. X-ray fluorescence (XRF) spectroscopy is proving to be a rapid, high-throughput method for analyzing venoms and is revealing several interesting compositional trends never before seen in venoms. Using XRF, we have analyzed the dominant elements found in snake venoms extracted from two species of rattlesnakes, Crotalus polystictus from central México and Crotalus viridis viridis from the eastern plains of Colorado USA. Notable in our findings were elemental differences within and between species, as well as between age and sex. Specifically, high concentrations of sulfur and potassium were found in both species, with calcium and zinc also present in moderate amounts. These elements are known to be associated with specific protein families (calcium and zinc are linked to snake venom metalloproteinases; sulfur: myotoxin and most other toxins). Also, potassium levels in neonate Crotalus polystictus were appreciably higher than that of their adults, and this metal's concentration in neonate Crotalus viridis viridis was 5-7-fold higher than that of adult snakes from the same population. High levels of potassium in neonate snake venoms, though not directly toxic, may potentiate toxic venom protein/peptide reactions in rodent prey by inducing hyperkalemia, leading to arrhythmia and cardiac arrest. While the functional significance of these differences is currently being explored, it is worth noting that metal elements, like the ones analyzed in this research, are required for metal-dependent enzymatic activities in snake venoms, some of which are being developed as biocatalytic drugs and therapeutic treatments. The data presented in this paper demonstrates that metal ions in snake venoms can vary as a function of species, sex and age of snakes, likely reflecting protein compositional differences and changes seen in these species.